While surfing the Strat's Place Living Wine Dictionary, I stumbled upon the following definition:

FINING
done to improve the clarity of a wine .. materials such as eggwhites (used for red wines), isinglass*( used for white wines), bentonite* are often used .. but believe it or not .. gelatin and even refined beef blood is used at times.

Basically these agents grab a hold of the loose particles that might cloud a wine and pull them to the bottom of the barrel.

Beef Blood? OK...maybe I'm thinking a bit too much but if there a remote possibility of developing mad cow disease from drinking wine that's undergone "fining" using refined beef blood.

PARIS - French health inspectors have seized 66,000 litres of Rhone Valley wine that may have been treated with oxblood powder, banned in the European Union since the 1997 mad cow disease scare, officials said on Thursday. [This apparently means that the French used this product throughout the BSE epidemic, 1984-1999 -- webmaster]

Gerard Bedos, head of the state regional consumer watchdog in Marseille, said inspectors seized the wine and 220 kg (480 lb) of powdered oxblood in the region around Avignon earlier this month. Bedos told the newspaper France-Soir the wine was being tested to determine whether it had been treated with oxblood.

He made it clear that the wine was labelled as lesser-quality VDQS table wine and not the renowned Cotes-du-Rhone wine which bears the high-quality AOC (Appellation d'Origine Controlee) label. Dried oxblood was routinely used to purify wine until the EU banned it two years ago in a health scare over the cattle disease.